The overall objective of our experiments is to alter in specific ways the mammalian cell phenotype by manipulating the hexose environment. The assumption is made that the oligosaccharide composition of cells, hence the composition of their glycolipids and glycoproteins is dependent to some extent upon the specific pool of nucleotide sugars in the cells. We have good evidence that the pool of nucleotide sugars can in fact be modified both by the sugars fed to cells and by nucleoside analogues. As well we have demonstrated that growth on specific sugars in lieu of glucose results in marked changes in: (1) hexose transport; (2) concanavalin A binding capacity; (3) average length of oligosaccharides in surface glycoproteins; (4) morphology and surface architecture of cells as revealed by scanning electron microscopy. The use of sugar analogues or nucleoside analogues, or both, might result in differential glycosylation or oligo-saccharide synthesis by cells. We hope to exploit the potential variation in glycosyl-transferase enzyme properties (including specificity for substrate and carrier) to reduce selectively the malignancy or increase the immunogenicity of tumor cells in situ.